Products and methods for producing detectable warnings for the visually impaired on various surfaces, such as pedestrian access areas, have been available for some time. For example, U.S. Pat. No. 5,385,770 describes a product with a repeating pattern of raised protrusions on a surface which has tactile and visual characteristics of detectable warnings which contrast with tactile and visual characteristics of surrounding surfaces.
U.S. Pat. No. 6,890,124 discloses a pre-cast detectable warning tile system for visually handicapped persons and which is intended for placement on walkways, crosswalks and other areas of pedestrian traffic. The tile is made for embedding in fresh concrete on a walking surface, and includes substantially planner top and bottom surfaces with the top surfaces having a plurality of raised elements configured as truncated dome structures and the bottom surfaces being scarified. The tiles can be provided as both angled planar cut pieces and rectangular planar pieces which can be placed or aligned together without being interconnected to form a walking surface which is flush to the edge of a walking surface.
International Patent Application No. PCT/US01/03964 discloses a detectable warning and wayfinding system for the visually impaired or handicapped which comprises a non-slip material, such as silicon carbide, to provide surface texture, and which also contains ridges and elongated truncated domes for detectability in pedestrian locations.
In another example, U.S. Published Patent Application No. 2005/0066623 discloses embedment tile for producing a tactilely detectable surface in concrete or asphalt which comprises a tile member substantially planar in form, and which has a pattern of upwardly extending projections on its upper surface forming a tactilely detectable pattern, such as useful for a warning or wayfinder means or for decoration, etc. The lower surface of each tile member comprises two or more cross-beams with hollow channels and end openings, and optional apertures to enable flow of concrete and air in and around the cross-beams to facilitate rapid installation. There may also be support members which project down further than the cross-beams and which function for support and to interlock the embedment tile to the concrete or asphalt once such material sets and hardens. Further, the sidewalls of the cross-beams may be V-shaped in cross section to facilitate their embedding in wet concrete or asphalt by moving such material into and around the cross-beams for an efficient insertion.
Additional examples include, for instance, a tactile identification and direction guidance system disclosed in U.S. Published Patent Application No. 2003/0037720; embedment tiles for pedestrian platforms and walkways provided in U.S. Pat. No. 5,775,835; a marking system for pedestrian crossings as disclosed in International Patent Application No. PCT/DK93/00272; and transit boarding panels as disclosed in U.S. Pat. Nos. 6,895,622 and 6,449,790.
The problem with many, if not all, of these products designed for embedment in sidewalk, street or other pedestrian walkway material, such as concrete and asphalt, however, is the difficulty in replacing broken tile units which degrade from use or other collisions, such as with snow removal equipment, end-loader buckets and the like. Many of these products have substantial pockets of trapped air formed under their walking surfaces during installation, and which can contribute to fracturing and other breakage during use over time, thereby rendering a once safe and helpful surface dangerous and requiring its replacement. Oftentimes replacement is only accomplished by time consuming and expensive labor intensive fracturing of the embedding concrete or other material, such as with a jackhammer, to remove broken or fractured tiles for their replacement. Due to the importance of such identification and wayfinding materials for handicapped people and their necessary existence and upkeep, more durable products and methods for their installation have long been needed.